The invention relates to a belt retractor for a vehicle seat belt, comprising a frame provided with a plurality of blocking teeth, a belt reel rotatably supported in the frame and a blocking tooth system adapted to be engaged with the blocking teeth, a control lever being pivoted on the frame and accommodating the belt reel and a sensor that actuates when a predetermined vehicle deceleration is exceeded.
In this type of belt retractor the belt reel is displaced, when it is to be blocked, relative to the frame so that the tooth system attached thereto engages with the blocking teeth provided on the frame. For this purpose, a control mechanism is provided to ensure that the tooth system of the belt reel is controlled to engage at the correct position in the blocking teeth so that an engagement of the tooth system in the blocking teeth is produced before high loads are acting on the belt reel.
For the webbing-sensitive blocking the control mechanism includes a control lever usually provided with an internal tooth system in which a control pawl arranged at an end face of the belt reel can engage. In the case of webbing-sensitive release the control pawl is pivoted outwardly from a home position by exploiting mass inertia forces such that it engages in the internal tooth system. Thus the belt reel is no longer freely rotatable but is coupled to the control lever.
For vehicle-sensitive blocking the control mechanism includes a coupling disk connected to the belt reel in a rotationally fixed manner. A sensor lever engages in the coupling disk when the sensor actuates upon a predetermined vehicle deceleration being exceeded. Thus the belt reel cannot freely rotate any longer.
When in such case, i.e. when the belt reel is no longer freely rotatable, tensile force is exerted on the webbing, this results in the control lever pivoting together with the belt reel about the pivot point at which the control lever is arranged on the frame and the belt reel is controlled to engage in the blocking teeth on the frame. The arrangement of the teeth of the internal tooth system at the control lever and the teeth of the coupling disk relative to the blocking teeth ensures that the belt reel is basically guided with its tooth system at the correct position into the blocking teeth so that the tooth crests of the tooth system of the belt reel are prevented from impacting on the tooth crests of the blocking teeth.
It is a drawback of the described lock mechanism that in a dynamic vehicle-sensitive activation of the blocking mechanism the coupling disk can twist or deform relative to the tooth system of the belt reel which results in the fact that the association of the blocking teeth with the tooth system of the belt reel cannot be precisely maintained any more. This may result in the fact that the tooth system of the belt reel is not controlled to engage at the correct position in the blocking teeth and the final engagement is brought about already under load.